You have a central thermostat built into the hypothalamus in the base of the brain. This co-ordinates thermogenesis (heat production) and heat loss (sweating and vasodilatation) to maintain an even operating temperature. When you become ill the hypothalamus turns up the thermostat in response to inflammatory substances, termed pyrogens, produced by the immune system. Paracetamol, and other anti-inflammatories, achieve their temperature-lowering effect by blocking the production of these factors, triggering the hypothalamus to reset body temperature to normal, making you feel better.

Chris

"I never forget a face, but in your case I'll make an exception" - Groucho Marx

Thanks Chris. That nicely answered my 2nd & 3rd questions. But what about the 1st 1?I infer from your answer that the body produces enough heat for our temperature to be a lot higher than it is (I'd always assumed it was the infection that caused the rise in body temperature). So why is our body temperature what it is? Is it the optimum temperature for some of the chemical reactions to take place?I know the testes need to be cooler than body temp; so do the other organs need the temperature to be exact for them to work peoperly?

The reason that you feel ill if your temperature rises only slightly higher is that we are chemical beasts and entirely dependent on chemical reactions. The rate of a chemical reaction is dependent on temperature, and different reactions are affected differently, so if you overheat some unwanted reactions get faster and vice versa, as you can imagine this will cause many problems...

I guess the problem is compounded by the fact that we have been warm blooded for a hundred million years or so, which means we have evolved to assume that we are at a certain temperature - a cold blooded animal would be more tolerent of different temperatures.

A lot of the reason that we get a temperature when ill is that most disease organisms are less tolerent of high temperatures than we are, so it is worth screwing ourselves up a bit if you can kill the bugs.

Can I assume from your reply that we're the temperature we are because that is the optimum temperature for the chemical reactions going on inside us? There's something about that that's niggling at the back of my mind, but I'm not sure what it is yet. I'll kick it around in the murky recesses of my mind for a while & see what pops out.

Alligators and crocks maintain their body temperature by altering their posture on a sloping river bank. Snakes and lizards are also able to use postural changes to alter their body temperature. Dinosaurs are now thought to have been warm blooded reptiles, which due to their adapted more upright posture could well have been harnessing the same effects.

Humans, when sleeping flat are known to have a drop in body temperature at around 4.30 am of some 2 degrees, I think this is also recorded in the U.K. as the time that most people pass away.

When the bed is raised by six inches at the head end, the body temperature appears to remain stable throughout the full bed rest period.

How do you account for this using the chemical reactions mentioned earlier?

"The explanation requiring the fewest assumptions is most likely to be correct."K.I.S. "Keep it simple!"

The reason that altering the angle of a cold bloodied animal will alter the body temperature, is that it will alter how much heat from the sun that they absorb, which will alter their temperature. Unless your sleeping subjects were doing so during the day, outside this is unlikely to be the reason that their temperature is altering.

It is natural that your body temperature reduces when asleep, this is probably to save energy. Your body temperature can be altered by slightly altering the temperature control system in the hypothalamus slightly.

It is quite possible that raising one end of a bed affects how your body is functioning slightly. I have definitely heard that it can reduce snoring considerably, which could ease breathing and therefore sleep. I am sure a medic could come up with many more possible mechanisms.

Alligators and crocks maintain their body temperature by altering their posture on a sloping river bank. Snakes and lizards are also able to use postural changes to alter their body temperature. Dinosaurs are now thought to have been warm blooded reptiles, which due to their adapted more upright posture could well have been harnessing the same effects.

Humans, when sleeping flat are known to have a drop in body temperature at around 4.30 am of some 2 degrees, I think this is also recorded in the U.K. as the time that most people pass away.

When the bed is raised by six inches at the head end, the body temperature appears to remain stable throughout the full bed rest period.

How do you account for this using the chemical reactions mentioned earlier?

Andrew - have you got the references for this, I'd like to read about it.

As I haven't seen the research that is being cited, I can only speculate as to why this observation might take place.

One explanation might be that when sleeping in a head-raised position there is a great venous pooling of blood in the legs and consequently a reduced venous return. To combat this, and maintain cardiac output, the tone of the sympathetic nervous system is raised to promote veno-constriction, with the side-effect of also stimulating other sympathetic processes such as metabolic rate. As a result more heat is produce, abolishing the natural nocturnal dip.

As I say, this is pure speculation as I've not seen the original research which, hopefully, Andrew can provide (please).

Chris

"I never forget a face, but in your case I'll make an exception" - Groucho Marx

ROBERT

Yeah pretty much, being products of evolution i am sure there is a whole lot of other things in the optimisation process, and the chemical reactions will have evolved for the temperature we are at.

An interesting thing is that the production of sperm works best at about 30C not 37C which is why testicles are on the outside, to keep them cool.

Another example of temperature driving evolution is alligator gender:-""Sex of alligators is determined by nest temperatures during the middle third of embryo development. Females are produced at temperatures less than 31.5oC; mixed sex ratios occur at 32oC, and males only are produced when temperatures are between 32.5 and 33oC. Decreasing numbers of males are produced as temperatures approach 35oC, a temperature beyond which only females are produced.""http://www.csc.noaa.gov/acebasin/specgal/gator.htm

Hi Chris, the experiment is easily replicated to prove what I have stated about temperature and sleep. The graph on this link provides the stats from taking mouth temperatures sleeping inclined compared to mouth temperatures sleeping flat.

Have recently stayed away from home with wife for a couple of days and can add definitely colder sleeping flat, skin cold to touch in the mornings, whereas skin nice and warm to touch in mornings sleeping inclined.

Humans, when sleeping flat are known to have a drop in body temperature at around 4.30 am of some 2 degrees, I think this is also recorded in the U.K. as the time that most people pass away.

When the bed is raised by six inches at the head end, the body temperature appears to remain stable throughout the full bed rest period.

How do you account for this using the chemical reactions mentioned earlier?

Andrew - have you got the references for this, I'd like to read about it.

As I haven't seen the research that is being cited, I can only speculate as to why this observation might take place.

One explanation might be that when sleeping in a head-raised position there is a great venous pooling of blood in the legs and consequently a reduced venous return. To combat this, and maintain cardiac output, the tone of the sympathetic nervous system is raised to promote veno-constriction, with the side-effect of also stimulating other sympathetic processes such as metabolic rate. As a result more heat is produce, abolishing the natural nocturnal dip.

As I say, this is pure speculation as I've not seen the original research which, hopefully, Andrew can provide (please).

Chris

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"The explanation requiring the fewest assumptions is most likely to be correct."K.I.S. "Keep it simple!"

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